Melanin is a pigment that is distributed widely in bacteria, fungi, plants and animals (1). Melanogenesis is initiated with oxidation of L-tyrosine by tyrosinase that is rate-limiting step in this process. Next reactions can proceed spontaneously (2). Tyrosinase that is a key enzyme in formation of melanin pigments, widely exists in animals and plants. Tyrosinase have a monophenolase activity as well as diphenolase activity that oxidizes o-diphenols to o-quinones (3). This study evaluated inhibitory effect of four plants including Physalis alkekengi L., Alcea rosea L., Bunium persicum B.Fedtsch. and Marrubium vulgare L. on mushroom tyrosinase. In this study L-Dopa (Dihydroxyphenilalanin) is used as substrate, so diphenolase activity of mushroom tyrosinase was evaluated. kojic acid was used as possitive control. Extracts of physalis alkekengi, Alcea rosea, Bunium persicum (Total), Bunium persicum (defatted) and Marrubium vulgare showed IC50 values of 0.09, 0.38, 0.37, 0.38, 2.76mg/ml respectively. IC50 values were defined as concentration of inhibitor that inhibited 50% of tyrosinase activity (4). Etract of Physalis alkekengi showed greatest inhibitory effect on mushroom tyrosinase activity with IC50 value of 0.09mg/ml. Kinetic and Inhibition parameters (Km, Vm, Ki) were calculated. In this study kinetic parameters (Km, Vm) are evaluated and Ki evaluated for P. alkekengi, A. rosea and B. persicum. Data has revealed that these three plants display a mixed- type inhibition. However Marrubium vulgare shows an uncompetitive inhibition (Table1). P. alkekengi that had the greatest tyrosinase inhibitor showed Ki value of 0.52mg/ml comparing another study on total extract of Lavandula stoechas L. showed Ki value of 0.183mg/ml (4). Finally calculation methods, types of inhibition (herbs & pure compounds) will be discussed.
Table 1: effect of Extracts and kojic acid on the kinetic parameters of mushroom tyrosinase.
|
|
N.I(a)
|
Kojic acid (b)
|
Physalis alkekengi
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Alcea rosea
|
N.I
|
Bunium persicum
|
Bunium persicum (defatted)
|
N.I
|
Marrubium vulgare
|
|
Km(mM)
|
0.18
|
0.45
|
0.22
|
0.3
|
0.11
|
0.17
|
0.13
|
0.14
|
0.12
|
|
Vm(U)
|
4.5
|
2
|
1.5
|
2.2
|
4.1
|
1.6
|
1.5
|
4.1
|
2.1
|
Keywords:
physalis alkekengi, Alcea rosea, Bunium persicum, marrubium vulgare, Tyrosinase, Inhibitor, Kinetic
References: 1. Kima Y-J et al. (2005) CMLS Cell Mol Life Sci 62: 1707–1723
2. Chang T-S (2009) International J Molecular Sci 10(6): 2440–2475
3. Wanga Q et al. (2007) Bioorganic & Medicinal Chemistry 15(3):1568–1571
4. Hsu C-K et al.(2007) Food Chemistry 105(3): 1099–1105
